1. Field of the Invention:
The present invention is a method and device (1) to determine precisely the three-dimensional coordinates of a target located internally within a visibly opaque but x-ray discernible object (e.g. a surgical patient) using x-ray fluoroscope imaging and (2) to use the determined coordinates to define a guiding path to reach the target location. The invention is useful in needle and drill placement for medical/surgical application such as highly localized chemical injection, biopsy, and orthopaedic procedures involving the bone. The specific use described relates a guide for correct positioning of a needle into the space adjacent a ruptured vertebrae disk for chemonucleolysis.
2. The Prior Art:
Chemonucleolysis is a method of healing ruptured vertebrae disks in which a surgeon injects chymopapain enzyme into the disk space. It is believed that the enzyme dissolves nucleus mucoproteins, which aids in healing ruptured vertebrae disks. Smith, U.S. Pat. No. 3,320,131 (1967) discloses in general terms the use of injected chymopapain for treating herniated intervertebral disks.
Typically, a surgeon makes an opening in the skin and attempts to position the probe properly and at the correct angle such that it contacts the disk to be treated. Some prior art guides, which are discussed below, have been used, but the positioning of the probe is frequently a manual operation. Once the probe is correctly positioned, a precise amount of chymopapain or other dissolving enzyme is injected through the probe into the desired location. The probe is usually positioned under a fluoroscope so that the surgeon can determine the location of the probe. He or she is given little leeway because the relatively strong muscles in the back limit movement of the probe once it is inserted through muscle tissue. Therefore, if the probe does not reach its desired location, it must be removed substantially from below the skin, and it must be reinserted at a new opening. Some very skilled and experienced surgeons can cause the probe to change directions below the skin and to locate the treatment site easily, but only one who is expert in this field has the required practice and skill.
As with any surgical procedure, there are risks. The principal one in chemonucleolysis is having the probe reach and thus damage the spinal cord or nerves exiting from the spinal cord between the vertebrae.
Workers designing surgical instruments have recognized that a device for positioning the needle guide in chemonucleolysis would be advantageous. Froning, U.S. Pat. No. 3,941,127 (1976) teaches a needle guide in which the device is taped to the patient and two vertical supports hang down along the patient's back. A chain hangs vertically downward from an arm attached to an assembly extending between the horizontal supports. The chain is positioned to be in line with a disk space between adjacent vertebrae into which the chymopapain is to be injected. A needle guide support is aligned with the chain and extends upward from a horizontal member also held by the vertical supports and carries a needle guide mounted at a 45.degree. angle to vertical. The needle guide can have one of a number of different sleeves to move up or down on the upward support, and the size of the sleeve is chosen in a procedure that takes place before the actual surgery. The bottom of the sleeve is aligned with an x-ray marker at the center of the spine. The distance from the bottom of the sleeve to the needle and from the sleeve inward to the center of the spine should be equal. This unit suffers because it is attached to the patient, which requires taping and leveling. For accurate distance and angle of entry, the x, y and z axes must be fixed. By using the patient as a reference surface, it is difficult for Froning to set reference axes. It also does not readily determine the horizontal distance to the midsaggital plane. Froning, U.S. Pat. No. 3,964,480 (1976) adds indexing to the sleeve and to the angled needle guide for calculating the location to insert the probe beneath the skin, but some of the aformentioned drawbacks still exist.
There are other devices used to locate a part of a surgical instrument to an area below the skin. Examples of some of these systems include Volkman, U.S. Pat. No. 3,115,140 (1963), Stenvall, U.S. Pat. No. 3,016,899 (1962), Barbier, U.S. Pat. No. 4,360,028 (1982) and Zukowski, U.S. Pat. No. 4,390,018, (1983), which is particularly directed to spinal procedures. In addition, Froning, U.S. Pat. No. 3,875,595 (1975) also relates to intervertebral disk prosthesis.
It is an object of the present invention to disclose and provide a method and apparatus for locating a target object within a visually opaque but x-ray transparent object using a fluoroscope and to determine a proper path that a needle, probe or drill takes to reach the target object. A narrow object primarily for chemonucleolysis, but the one described with reference to the exemplary embodiment is to locate the disk space (target object) in the patient (opaque object) and to determine the correct angle for the needle to reach the disk space.
Another object of the present invention is to disclose and provide a device that is free standing and does not have to be attached to the object (e.g. patient) in which the target object is located. Another object is to disclose and provide a device that will locate the needle guide at the proper location beneath the skin in a combined, easily performed operation in which the same device can be used to measure the horizontal distance from the device to the midsaggital plane, which distance is needed for proper positioning of the needle and probe support.
These and other objects of the present invention will be evident from the more detailed description of the invention.